A class B push pull power amplifier uses transistor of dissipation

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A class B push pull power amplifier uses transistor of dissipation capability of 2 watts per transistor. For maximum possible a.c. power output from the system,
the reflected transformer primary resistance when
V_CC = 20 volts is given by:

1. 100 ohms
2. 50 ohms
3. 20 ohms
4. 12.5 ohms

Correct Option: C

Given that power dissipation capacity = 2 watts for each transistor so total power dissipation
= 2 × 2 = 4 Watts.
P_{D (max)} ≈ 0.4 P_{o (max)}
4 ≈ 0.4 P_{o (max)}

or P_{o (max)} =	4	= 10
	0·4

Now, P_{o (max)} =	V²_m
	2R_L

or R_L =	V²_m	=	20²	= 20 Ω
	2·P_o(max)		2 × 10